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| Titel |
Impact of land use change on soil organic matter dynamics in subalpine grassland |
| VerfasserIn |
Stefanie Meyer, Jens Leifeld, Michael Bahn, Jürg Fuhrer |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250032254
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| Zusammenfassung |
| Information regarding the response of soil organic matter (SOM) in soils to past and expected
future land use changes in the European Alps is scarce. Understanding this response requires
knowledge of size and residence times of SOM fractions with distinct stabilities. In
order to quantify differences between types of land use in the amount, distribution
and turnover rates of soil organic carbon (SOC) in subalpine grassland soils, we
used soil aggregate and SOM density fractionation in combination with 14C dating.
Samples were taken along gradients of different types of land use from meadow
(M) to pasture (P) and to abandoned grassland (A) in the Stubai Valley and in the
Matsch Valley. Sampling sites in both areas were located at equal altitude (1880
m and 1820 m, respectively) with the same parent material and soil type, but the
Matsch Valley receives 400-500 mm less annual rainfall. SOC stocks in the top 10
cm were 2.47 ± 0.32 (M), 2.75 ± 0.32 (P), and 2.50 ± 0.31 kg C/m2 (A) in the
Stubai Valley and 2.25 ± 0.14 (M), 3.45 ± 0.22 (P), 3.16 ± 0.27 kg C/m2(A) in
the Matsch Valley. Three aggregate size classes were separated by wet sieving:
2Â mm. The light floating fraction (wPOM, Ï >1Â g/cm3) was included in
the analysis. Free (f-) and occluded particulate organic matter (oPOM) were isolated
from each aggregate size class (Ï >1.6 g/cm3). At both locations, more than 80%
of SOC was stored in small (0.25-2 mm) and large (>2 mm) macroaggregates,
but no trend in relation to the different types of land use could be detected. The
fraction of C in fPOM and in oPOM in all aggregate size classes was highest for
soil from abandoned grasslands. The bulk soil of the abandoned site in the Stubai
Valley showed a significantly higher share of fPOM-C and oPOM-C and a higher
amount of wPOM-C as compared to the soil from managed grassland, whereas in the
Matsch Valley pasture soil had a significantly higher wPOM-C content. At both
sites, 13C natural abundance analyses revealed a gradient in 13C between density
fractions. wPOM was particularly useful to reveal differences between sampling sites.
Radiocarbon values emphasized the importance of this fraction for the calculation of the
turnover of bulk soil C. wPOM turned out to be the most active fraction turning
over in 2-4 years. Bulk SOC turnover time was approximately 46 years for pasture
soil and 78 years for meadow soil. In conclusion, density fractionation produced
homogenous fractions allowing detection of differences between different land use
types. However, C distribution among aggregates did not systematically differ. |
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